HU''''ONG DAN QUAN LI SU DUNG GlAl DAP MOT SO Difeu KHI DAY HOC SINH THUC HANH BAI MAY BlfeN THE Trong thdi gian qua, mgt so giao vien (GV) d cdc tinh Hda Binh, San La, Gia Lai, Ben Tre, cd ggi di^n ve h[.]
HU'ONG DAN QUAN LI SU DUNG GlAl DAP MOT SO Difeu KHI DAY HOC SINH T H U C HANH BAI: MAY BlfeN THE Phgm Dinh Cuoug T rong thdi gian qua, mgt so giao vien (GV) d cdc tinh: Hda Binh, San La, Gia Lai, Ben Tre, cd ggi di^n ve hdi mgt so van de ve thi nghipm vgt ly d trudng trung hgc co sd Trong bdi xin gidi ddp mgt so van dl quanh vipc gidng dgy vd cho hgc sinh (HS) thye hanh bdi; Mdy bien the I Mgt sl cdu hdi ciia dgc gia ve bai: May bien thi Trong saeh giao khoa ldp cd viet: Hieu dien the d hai dau mdi cudn ddy cua may bien the ti le vdi sd vdng day cua mdi cudn: U,/U, = n,/n, Nhung Idm thi nghiem vdi cdc ehi tiet bd dyng ey thi nghiem vat ly Idp da duae trang bi thi thay: U,/U, + n/n, Xin eho biet ly tgi sao? Bien the ngudn bd dung ey thi nghiem vat ly ldp de ehuyen mach d nde 6V thi ben xoay ehieu ddng hd chi 6V edn d ben mgt ehieu ddng hd chi ban 8V Nhu vgy cd phdi bien the lam khdng dung khdng? Bien the ngudn bg dyng cy thi nghiem vat ly Idp cd hidn tugng da ngdt ngudn nhung neu hipu dipn the d maeh mgt ehieu van cd Cd ngudi eho rang bien thi ngudn nhu vdy khdng dat yen cau, dieu dd cd dung khdng? Tai tien hanh mdt s6 thi nghipm vdi ede chi tilt cua bg dyng ey thi nghipm da dugc Bg trang bj, biln the hay bj ngdt dipn, khdng thyc hipn dugc thi nghipm? Bien thi nguon nhd trudng cd nac 12V mgt chieu cd the dung dk ngp cho ac quy 12V khdng? Ldm the nao de biet edng suit ciia biln thi tren biln thi khdng dl gi? Khi bien the nhd bi chdy, day quan bidn the rat nhd va bi ddt, khdng dem duge so vdng «220V Cau chi HI day, lam the ndo de bilt sd vdng ddy ma quin lai? De gidi dap cdc cau hdi tren, can biet ve eau tao cua bien the ngudn dung tinrdiig phd thdng Hinh Id so nguyen ly cda biln thi ngudn thudng diing trudng tiidng Miii ten Id tugng tnmg cho chuyin mgch de thay ddi dipn ap Dipn dp xoay chilu bdn thu cip duge dua hai chdt ed ky hidu ~ Dipn ap xoay ehieu dugc dua vao bd chinh luu dl trd Ngay nhdn bdi 9/6/2012 Ngdy duy?t dang 28/6/2012 38 • TAP CHI THIET BI GIAO DUC - SO 83 - 7/2012 thdnh mdt ehieu rdi den hai chot ed ky hi eu + vd - Ty C dl on dinh dipn dp mgt chilu sau chinh luu Tu C Id ty hda cd tri so cdng cao edng tdt vi ty cd trj so dipn dung cdng cao thi dipn dp mgt chilu edng on djnh Dipn trd R de an todn cho bg chinh luu khdng may mgch mgt chieu bi ngdn maeh Cau chi de bdo ve may bien thi qua tdi Bien thi bg dung cy thi nghiem vat ly ldp 7, vd THPT co mgeh ty dgng ngat dien vao bien the ddng dipn d mach thd cap len den 3A n Ddp an cho cac cau hoi trSn I.Tai ldm thi nghiem vdi bien thi bd dyng ey thi nghiem vdt ly thi tiiiy Uj/U^ ^,n/n,? Ta biet rang cd ddng dipn xoay chieu di qua eudn so cdp n, du nd tgo tu tmdng bien thien ldi thep cua bien the Trong loi thep d eudn thu cdp n^ ed tu trudng bien thien ndn d eugn n^ xuat hi$n sudt dien ddng cam iing Nang lugng dipn d eugn so cap n, chuyen sang eugn n^ bi tdn hao loi thep, cac cugn day ddng d bien the nen thyc tl khdng bao gid c6 U,/U2 = n/n2 Trong thuc tl Uj dugc nhd hon ly thuyet, nhdt la biln the dimg thyc hanh eho HS cd loi thep chit lugng khdng cao, day ddng cua cdc cugn day cd HUONG DAN QUAN LI SU DUNG TruSc chlnh liAi H2 Sau chinh liAi {chi/a co tu C) H3 \l W -J \i \i I M \l I W U !L_ t Sau chhh luu (c6 tu C) H4 tiet dien nhd nen dipn trd Idn vi vgy tdn hao ddng va tdn hao Idi thep nhieu vi the U^/ Uj nhd ban n^/n, nhieu: U,/U,